Dysregulation of apoptosis is involved in various pathological conditions. For example, many cancers are characterized by a defect in the apoptotic process, such that the number of dying cells in a tissue is decreased below its normal level, resulting in an imbalance of cell death and cell proliferation and consequent growth of a tumor. In addition, neurodegenerative diseases are believed to be caused, at least in part, due to the induction of apoptosis, which can result in death of neuronal cells.
Several gene products that modulate the apoptotic process have been identified. The Bcl-2 family of proteins, which plays an important role in regulating cell survival and cell death, can be divided into two groups, proapoptotic proteins (Bak and Bak) and antiapoptotic proteins (Bcl-2, Bcl-xL, A1, Mcl-1, and Bcl-w; Adams et al. Science 281: 1322-1326; Henson et al. Clin. Cancer Res. 12: 845-853). Antiapoptotic family member Mcl-1 (encoded by the MCL1 gene) was first characterized from a myeloid leukemia cell line (ML-1) induced to differentiate along the monocytic lineage (Kozopas et al. Proc. Natl. Acad. Sci. U.S.A. 90: 3516-3520; Leuenroth et al. J. Leukoc. Bioi. 68: 158-166) and has since been shown to be expressed in a wide variety of tissues and neoplastic cells and to influence the development of numerous malignancies (Thallinger et al. Clin. Cancer Res. 10: 4185-4191).
The role of Mcl-1 in regulating cell fate has made it a target of interest in many studies of apoptosis and hyperproliferative diseases. Many reports have demonstrated the importance of inhibiting Mcl-1 expression to increase apoptosis and regulate neoplastic disease (see, e.g., U.S. Pat. No. 6,800,750 and WO 94/29330), and inhibition of Mcl-1 expression has been proposed and/or shown to increase apoptosis, decrease cell viability and/or decrease tumor weight of normal cells, cancer cell lines or xenograft tumors.
Certain groups have previously identified MCL1 as a target for antisense oligonucleotide or siRNA-based agents (see, e.g., U.S. Pat. No. 6,001,750; Henson et al. Clin. Cancer Res. 12:845-853, which disclosed a Mcl-1 antisense oligonucleotide that sensitized breast cancer cell lines to apoptosis; Selzer et al. Mol. Med. 8:877-884, that disclosed inhibition of Mcl-1 expression in melanoma cells using an antisense oligonucleotide targeting Mcl-1; Skvara et al. Anticancer Res. 25: 2697-2703, which showed a Mcl-1 antisense oligonucleotide that sensitized human melanoma cells to ionizing radiation-induced apoptosis; Sieghart et al. J. Hepatol. 44: 151-157, that found the Mcl-1 to be overexpressed in hepatocellular carcinoma cell lines and disclosed a Mcl-1 antisense oligonucleotide that decreased protein expression, increased apoptosis, decreased cell survival and sensitized HCC cells to chemotherapy; Song et al. Cancer Biol. Ther. 4: 267-276; Aichberger et al. Blood 105:3303-3011, disclosed a Mcl-1 antisense oligonucleotide and siRNA which inhibited expression of Mcl-1 in chronic myeloid leukemia (CML) cells and decreased cell viability, and that the Mcl-1 antisense oligonucleotide synergized with a BCRI ABL inhibitor (Imatinib) to produce growth arrest; Derenne et al. Blood 100: 194-199 and Zhang et al. Blood 99: 1885-1893) disclosed use of Mcl-1 antisense oligonucleotide to decrease expression of Mcl-1, decrease cell viability and increase apoptosis of multiple myeloma cells lines and primary cells; Michels et al. Oncogene 23: 4818-4827; Sly et al. J. Immunol. 170: 430-437; Liu et al. J. Exp. Med 194: 113-126; Moulding et al. Blood 96: 1756-1763; Leuenroth et al. J Leukoc. Biol. 68: 158-166; Thallinger et al. Clin. Cancer Res. 10: 4185-4191, disclosed an antisense oligonucleotide targeted to Mcl-1 which decreased expression of Mcl-1 in sarcoma xenotransplants and when used in combination with cyclophosphamide, reduced tumor weight and increased tumor cell apoptosis; and Thallinger et al. J. Invest. Dermatol. 120: 1081-1086, which showed a Mcl-1 antisense oligonucleotide administered systemically with or without dacarbazine in a human melanoma SCID mouse xenotransplantation model to have decreased target protein expression, increased apoptosis and decreased tumor weight).
Double-stranded RNA (dsRNA) agents possessing strand lengths of 25 to 35 nucleotides have been described as effective inhibitors of target gene expression in mammalian cells (Rossi et al., U.S. Patent Application Nos. 2005/0244858 and US 2005/0277610). dsRNA agents of such length are believed to be processed by the Dicer enzyme of the RNA interference (RNAi) pathway, leading such agents to be termed “Dicer substrate siRNA” (“DsiRNA”) agents. Additional modified structures of DsiRNA agents were previously described (Rossi et al., U.S. Patent Application No. 2007/0265220).
Provided herein are improved dsRNA agents that target MCL1. In particular, DsiRNAs targeting MCL1 have been specifically exemplified.